Apply bsplines in element

Hello community,

I am currently working on non linear problems, for that i need to define a bspline in each element of a surface,for example
for el in elements

aEnergy += SymbolicEnergy(gfrho, definedon=mesh.Materials(material_name_to_study)) # formulation defined on 1 element

Is there a way to do this, because gfrho.vec take just a float not a bspline

Thanks in advance,

Best Regards,